PROJECT ABSTRACT Dengue virus (DENV) occurs as 4 serotypes that are biologically transmitted between humans principally by Aedes aegypti mosquitoes. This virus causes dengue fever, which is the most widespread and significant arboviral disease in the world. It also is the etiological agent of dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS), severe and sometimes fatal forms of the disease. At present, mosquito control remains the only option for preventing transmission to humans of dengue and several other arboviruses. A. aegypti is also a primary vector for Zika and chikungunya virus as well as yellow fever virus in urban areas, throughout the tropics and subtropics, and is a recognized model for innate immunity studies with both protozoan (malaria: Plasmodium gallinaceum) and metazoan (lymphatic filariasis: Brugia malayi) parasite infections. The long-term goals of this research are to identify, isolate, and characterize genetic factors conditioning the A. aegypti innate immune response to arbovirus infection. Our general hypothesis is that a very small number of key genes condition a susceptible or refractory innate immune response to DENV and likely to ZIKV and other pathogens as well. Our rationale for this research is that these genes once identified could provide a foundation to explore development of a next generation of targeted and effective genetic control strategies. Our project builds on extensive preliminary data as well as the existing whole genome assembly for A. aegypti. The project specific aim is designed to employ well-established methods to identify discrete genome regions defined as quantitative trait loci (QTL) containing key genes that condition arbovirus susceptibility and identify all genes within these regions for future targeted functional analysis. The proposed research is significant as we expect it to better inform our basic understanding of the innate immune system in A. aegypti, with an overarching goal to facilitate development of new genetic control paradigms. Our proposed research is innovative because for the first time, it will integrate genetic, genomic, and phenotypic information on the A. aegypti innate immune response to DENV and ZIKV infection as derived from well-characterized susceptible and refractory genetic stocks. We expect that knowledge gained in this R21 proposal will provide critical preliminary data to support future detailed research that has potential to significantly enhance our understanding of the fundamental innate immune responses that promote or prevent successful arbovirus infection in this critical vector species, and could provide a model for conducting similar research in other arthropod/pathogen relationships.